Dopaminergic-like cells from epigenetically reprogrammed mesenchymal stem cells

Combination of the modulators of epigenetic machinery and specific cell signaling pathways as a promising approach for cell reprogramming

During embryogenesis and further development, mammalian epigenome undergoes global remodeling, which leads to the emergence of multiple fate-restricted cell lines as well as to their further differentiation into different specialized cell types. There are multiple lines of evidence suggesting that all these processes are mainly controlled by epigenetic mechanisms such as DNA methylation, histone covalent modifications, and the regulation of ATP-dependent remolding of chromatin structure. Based on the histone code hypothesis, distinct chromatin covalent modifications can lead to functionally distinct chromatin structures and thus distinctive gene expression that determine the fate of the cells. A large amount of recently accumulated data showed that small molecule biologically active compounds that involved in the regulation of chromatin structure and function in discriminative signaling environments can promote changes in cells fate. These data suggest that agents that involved in the regulation of chromatin modifying enzymes combined with factors that modulate specific cell signaling pathways could be effective tools for cell reprogramming. The goal of this review is to gather the most relevant and most recent literature that supports this proposition.

Mesenchymal Stromal Cells Preconditioning: A New Strategy to Improve Neuroprotective Properties

Neurological diseases represent one of the main causes of disability in human life. Consequently, investigating new strategies capable of improving the quality of life in neurological patients is necessary. For decades, researchers have been working to improve the efficacy and safety of mesenchymal stromal cells (MSCs) therapy based on MSCs’ regenerative and immunomodulatory properties and multilinear differentiation potential. Therefore, strategies such as MSCs preconditioning are useful to improve their application to restore damaged neuronal circuits following neurological insults. This review is focused on preconditioning MSCs therapy as a potential application to major neurological diseases. The aim of our work is to summarize both the in vitro and in vivo studies that demonstrate the efficacy of MSC preconditioning on neuronal regeneration and cell survival as a possible application to neurological damage.

Comparison of the neuronal differentiation abilities of bone marrow‑derived and adipose tissue‑derived mesenchymal stem cells

Bone marrow-derived mesenchymal stem cells (BMSCs) and adipose tissue-derived mesenchymal stem cells (ADSCs) are able to differentiate into neuron-like cells when exposed to small molecule compounds, however the specific differences in their neuronal differentiation abilities remain to be fully elucidated. The present study aimed to compare the neuronal differentiation abilities of BMSCs and ADSCs. BMSCs and ADSCs from the same Sprague Dawley rats were isolated and cultured for use. The proliferation capacity was revealed using a cell counting method. Following BMSCs and ADSCs induction by four types of small-molecular compounds, the expression of various neuronal markers and the secretion of several neurotrophic factors were detected by immunofluorescence, western blotting, reverse transcription-quantitative polymerase chain reaction and ELISA. It was demonstrated that the ADSCs exhibited an increased proliferation capacity compared with BMSCs, according to cumulative population doubling analyses. Following a 7-day neuronal induction period, BMSCs and ADSCs exhibited a neuron-like morphology, and were termed neuronal induced (NI)-BMSCs and NI-ADSCs. They expressed neuronal markers including β-tubulin III, microtubule associated protein 2 and choline acetyltransferase. The number of NI-BMSCs that positively expressed the neuronal markers was significantly decreased compared with NI-ADSCs, and the expression and secretion of the neurotrophic factors nerve growth factor and 3′-nucleotidase in NI-BMSCs were additionally decreased compared with NI-ADSCs. The findings of the present study indicated that the neuronal differentiation abilities and neurotrophic factor secretion abilities of ADSCs were increased compared with BMSCs. ADSCs may therefore act as efficient candidates in cell transplantation therapy for diseases and injuries of the nervous system.

Fibroblast Growth Factor Receptor-2 Contributes to the Basic Fibroblast Growth Factor-Induced Neuronal Differentiation in Canine Bone Marrow Stromal Cells via Phosphoinositide 3-Kinase/Akt Signaling Pathway

Bone marrow stromal cells (BMSCs) are considered as candidates for regenerative therapy and a useful model for studying neuronal differentiation. The role of basic fibroblast growth factor (bFGF) in neuronal differentiation has been previously studied; however, the signaling pathway involved in this process remains poorly understood. In this study, we investigated the signaling pathway in the bFGF-induced neuronal differentiation of canine BMSCs. bFGF induced the mRNA expression of the neuron marker, microtubule associated protein-2 (MAP2) and the neuron-like morphological change in canine BMSCs. In the presence of inhibitors of fibroblast growth factor receptors (FGFR), phosphatidylinositol 3-kinase (PI3K) and Akt, i.e., SU5402, LY294002, and MK2206, respectively, bFGF failed to induce the MAP2 mRNA expression and the neuron-like morphological change. bFGF induced Akt phosphorylation, but it was attenuated by the FGFR inhibitor SU5402 and the PI3K inhibitor LY294002. In canine BMSCs, expression of FGFR-1 and FGFR-2 was confirmed, but only FGFR-2 activation was detected by cross-linking and immunoprecipitation analysis. Small interfering RNA-mediated knockdown of FGFR-2 in canine BMSCs resulted in the attenuation of bFGF-induced Akt phosphorylation. These results suggest that the FGFR-2/PI3K/Akt signaling pathway is involved in the bFGF-induced neuronal differentiation of canine BMSCs.

Epigenetic modulators promote mesenchymal stem cell phenotype switches

Discoveries in recent years have suggested that some tissue specific adult stem cells in mammals might have the ability to differentiate into cell types from different germ layers. This phenomenon has been referred to as stem cell transdifferentiation or plasticity. Despite controversy, the current consensus holds that transdifferentiation does occur in mammals, but only within a limited range. Understanding the mechanisms that underlie the switches in phenotype and development of the methods that will promote such type of conversions can open up endless possibilities for regenerative medicine. Epigenetic control contributes to various processes that lead to cellular plasticity and DNA and histone covalent modifications play a key role in these processes. Recently, we have been able to convert human mesenchymal stem cells (hMSCs) into neural-like cells by exposing cells to epigenetic modifiers and neural inducing factors. The goal of this study was to investigate the stability and plasticity of these transdifferentiated cells. To this end, neurally induced MSCs (NI-hMSCs) were exposed to adipocyte inducing factors. Grown for 24-48 h in fat induction media NI-hMSCs reversed their morphology into fibroblast-like cells and regained their proliferative properties. After 3 weeks approximately 6% of hMSCs differentiated into multilocular or plurivacuolar adipocyte cells that demonstrated by Oil Red O staining. Re-exposure of these cultures or the purified adipocytes to neural induction medium induced the cells to re-differentiate into neuronal-like cells. These data suggest that cell plasticity can be manipulated by the combination of small molecule modulators of chromatin modifying enzymes and specific cell signaling pathways.

Enhancing the efficiency of direct reprogramming of human primary fibroblasts into dopaminergic neuron-like cells through p53 suppression

Dopaminergic (DA) neuron-like cells obtained through direct reprogramming of primary human fibroblasts offer exciting opportunities for treatment of Parkinson's disease. A significant obstacle is the low efficiency of conversion during the reprogramming process. Here, we demonstrate that the suppression of p53 significantly enhances the efficiency of transcription factor-mediated conversion of human fibroblasts into functional dopaminergic neurons. In particular, blocking p53 activity using a dominant-negative p53 (p53-DN) in IMR90 cells increases the conversion efficiency by 5-20 fold. The induced DA neuron-like cells exhibit dopamine neuron-specific gene expression, significant dopamine uptake and production capacities, and enables symptomatic relief in a rat Parkinson's disease model. Taken together, our findings suggest that p53 is a critical barrier in direct reprogramming of fibroblast into dopaminergic neurons.

Enhanced dopamine release by mesenchymal stem cells reprogrammed neuronally by the modulators of SMAD signaling, chromatin modifying enzymes, and cyclic adenosine monophosphate levels

Recently, using the chemical genetics approach for cell reprogramming, via the combination of small molecule modulators of chromatin modifying enzymes, specific SMAD signaling pathways, and cyclic adenosine monophosphate levels, we have been able to generate neuronallike cells predominantly positive to mature neuronal and dopaminergic markers. This study aimed to characterize further the dopaminergic properties of neurally induced (NI) human bone marrow-derived mesenchymal stem cells (hMSCs) and to determine whether addition of sonic hedgehog (SHH)/fibroblast growth factor 8 (FGF8) to NI medium could promote further dopaminergic maturation. Dopaminergic differentiation was evaluated by immunocytochemistry, reverse transcription-polymerase chain reaction, Western blot, and enzyme-linked immunosorbent assay. Results demonstrated that release of dopamine by NI-hMSCs differentiated with SMAD inhibitor supplementation significantly increased from picogram to nanogram levels, with a tendency of further increase when supplemented by SHH/FGF8. Direct generation of dopaminergic cells from adult hMSCs by using this reprogramming approach may have significant implications for understanding the mechanism underlying cell plasticity and may open new potentialities for cell replacement therapies.

Enhancing the efficiency of direct reprogramming of human mesenchymal stem cells into mature neuronal-like cells with the combination of small molecule modulators of chromatin modifying enzymes, SMAD signaling and cyclic adenosine monophosphate levels

Advances in cell reprogramming technologies to generate patient-specific cells of a desired type will revolutionize the field of regenerative medicine. While several cell reprogramming methods have been developed over the last decades, the majority of these technologies require the exposure of cell nuclei to reprogramming large molecules via transfection, transduction, cell fusion or nuclear transfer. This raises several technical, safety and ethical issues. Chemical genetics is an alternative approach for cell reprogramming that uses small, cell membrane penetrable substances to regulate multiple cellular processes including cell plasticity. Recently, using the combination of small molecules that are involved in the regulation chromatin structure and function and agents that favor neural differentiation we have been able to generate neural-like cells from human mesenchymal stem cells. In this study, to improve the efficiency of neuronal differentiation and maturation, two specific inhibitors of SMAD signaling (SMAD1/3 and SMAD3/5/8) that play an important role in neuronal differentiation of embryonic stem cells, were added to our previous neural induction recipe. Results demonstrated that human mesenchymal stem cells grown in this culture conditions exhibited higher expression of several mature neuronal genes, formed synapse-like structures and exerted electrophysiological properties of differentiating neural stem cells. Thus, an efficient method for production of mature neuronal-like cells from human adult bone marrow derived mesenchymal stem cells has been developed. We concluded that specific combinations of small molecules that target specific cell signaling pathways and chromatin modifying enzymes could be a promising approach for manipulation of adult stem cell plasticity.